Spark plug and method of making the same



Novl 12,1935.

0. c. RoHpE SPARK PLUG- AND METHOD Of MAKING THE SAME Filed Sept. 21, 1934 FEE-1E.

m l. m

FTC-=15- Patented Nov. 1935 PATENT OFFICE SPARK PLUG AND METHOD OF MAKING THE SAME o. Bohde, Toledo, Ohio, assignor to Champion Spark Plug Company, Toledo, Ohio, a corpora'tion of Delaware September 21,1934. Serial No. 744,949

1 s Gains. (oi. za-w 'lhis application relates to a spark plug and method of making the same. More particularly it relates to a novel method of securing an electrade in a spark plug core and the core in the I, shell, and the structure resulting from this method.

' Considerable difiiculty has been encountered in satisfactorily sealing the central electrode in the usual spark plug core of porcelain or the like, and

I in permanently securing thecore in its metallic shell. Thwe dimculties arise from the differences between the materials of which the several parts are made and their action under the tryi heat i variations to which a spark plug is subjected in In my co-pending application for Spark plug and method of making the same, filed February 9, 1934, Serial No. 710,459, I have disclosed and claimed an improvement whereby the electrode I) is sealed in the core by compacting soapstone or the like around the electrode in the core of the I bore. By my present improvement I have simplilied and somewhat improved the sealing of the electrode in the core, and likewise have provided 5 for a similar sealing of the core in its shell. This improvement comprises as an important element the use of a compacting powder having a'relatively low angle of repose, as will be pointed out more-fully as the description proceeds.

i In the accompanying drawing, Figure 1 shows a spark plug, partly in section and embodying certain features of my invention. Figs. 2 and 3 are .c sectional views of powder-testing 'means showing different angles of repose of powder.

In Fig. 1 there is shown the usual spark plug ceramic core I. having a shoulder I l seated upon agasket ii on the shoulder I: of the usual shell I. Above shoulder ii the core'is shown as be substantially cylindrical, and the bore of the shell is substantially cylindrical from shoulder 3| t6 an upper inturned flange l5. Beneath flange ll there is a sealing ring I. Beneath ring it and above shoulder I l the space between the core and the-shell is filled with compacted powder II, which will be more fully described later.

The central electrode i8 is provided with a shoulder I! which rests upon a shoulder II in the central bore of the core. compacted powder 50 2 l within the bore around the electrode and above the shoulder is seals theelectrode in place, in a manner similar to that disclosed in my aforesaid co-pending application.

The powder I use for sealing the electrode in I the core and the core in the shell must lie-readily fed into the space tobe filled and must be compactible by a permissible amount of pressure into a sealing body holding the parts in their respective positions and forming gas-tight joints. and

seals. As indicated in the aforesaid co-pending ii case, powdered soapstone is a material having these qualities.

I have discovered that other powdered mineral materials may be used that contain combined water but are dry so far as free water is 10 concerned, and that do not lose water when heated to the temperature to which the several joints of the plug are subjected in regular use. Many materials have been tested and there are so few, if any, materials within the above definition 16 that cannot be compacted into an operative seal that the above definition appears to be a statement of the operative material sufficiently accurate for practical purposes.

The difliculty with powders of the kind de- 20 scribed is that, even when rendered bone dry, so far as free water is concerned, by ordinary methods, the powder still has an undesirably high angle of repose. Of course any appreciable amount of free water in such powder interferes with its pouring. For my purposes, a relatively low angle of repose is very advantageous.

Not only does a low angle of repose greatly facilitate the feeding of the powder into the space in which it is to be compacted, but it aids 80 in the uniform filling of such a space and lessens the danger of bridging during compacting. Where the powder has a high angle of repose, the attempt to compact any great depth in a narrow space isapt to result in bridging, that is, the compacting of an upper portion of the powder and its pressure against the adjacent 'wallssufiiciently so that it is supported by friction on the walls and does not transmit pressure to the powder therebeneath. Under such 40 circumstances only the upper part of the powder is thoroughly compacted. Accordingly only a relatively shallow layer can be compacted at one time when the powder has a high angle of repose. A

When the powder has a relatively low angle of repose, it acts more like a liquid during the initial stages of compression, and so is formed into a relatively uniform body before the final compression is applied.. As a consequence, a deeper layer in proportion to, its width can be compressed at one operation.

InFig. 2 there is shown a section of a box 25 having therein powder 26. Oneend 21 of the boxis shown open, and, as indicated, the powder runs out to a plane indicated at 28. This illustrates approximately the result with ordinary manner.

However, soapstone powder or the like may be treated, as by spray drying, so that it has an angle of repose of under 45". In Fig. 3 there is illustrated a box having therein powder II, with one end 32 of the box open. Powder 3| has been treated so that it has an angle of repose less than and, as illustrated, where the angle is less than 45 the surface 33 of the powder closely approximates a true plane, and tilting of the box results in a much more even fiow of the material until the surface is restored to the proper angle, with much less tendency to avalanch than when the angle of repose is higher.

It will be readily seen that such powder may be much more uniformly filled into a narrow space to considerable depth than where the angle 'of repose is higher.

For satisfactory work in sealing electrodes into cores, I prefer to prepare the powder so that it has an angle of repose somewhat less than 45. I have used with much success powdered soapstone treated and spray-dried so that it had an angle of repose of the order of 30'. While continued reduction of the angle of repose below 45 is helpful, it does not have as important an eiiect upon the behavior of the powder as does the more critical change in the angle of repose from above to below 45.

. Powder oi the kind described may be readily filled into the narrow space around the electrode, as well as between the core and shell, and may be compressed in a body which forms a gas-tight joint and frictionally engages the adjacent walls sufliciently to hold the assembled parts in place, and the compacted body has suf-' ficient resiliency to maintain a tight joint between the parts throughout the repeated temperature changes to which the plug is subjected in use, and without imposing undue stresses upon the parts because of diiferent coefiicients of heat expansion.

- It is undesirable to permit access'of moisture to the compacted powder, and therefore it is desirable to provide a substantially water-proof seal above the compacted powder. This may be done in various obvious ways.

A particularly desirable method of sealing the space above the powder between the core and shell is shown in Fig. 1, where the seal is made .by ring ll held in place by flange l5, but it should be understood that the ring and flange are employed only for se i g the top of the space against the entrance of water or other injurious material, since the compacted powder securely holds the core and shell in assembled relation with .a constantly gas-tight joint, the powder gripping the shell and core sufiiciently for this purpose. Obviously, other means may be substitutedfor protecting the joint from water, and

Y other obvious changes may be made within the scope of the appended claims.

What I claim is:

L'The method of securing a ceramic spark plug core in a metallic shell which comprises assembling the core and shell in concentric relation with an annular space therebetween, filling i said space with compactible powder, and compacting the powder until it forms a uniting body gripping the opposing walls of the parts and forming a gas-tightseal therebetween.

2. The method of securing together a conduoit tor and a ceramic insulator, which comprises assembling the conductor and insulator in concentric relation with a narrow annular space therebetween, pouring into said space a non-metallic mineral powder, dry as to free water, containing ll water of combination, and having an angle of reposeoi not over 45", and compressing the powder in the space with suflicient force to compact it into a permanent holding body forming a gas tight joint with the opposed surfaces of the insu- 20 lator and conductor, the filling and compressing being in successive layers which are sufllciently shallow to result in substantially uniform compacting of the powder without bridging.

3. The method of securing an electrode in a 25 rigid spark plug core, which consists in assembling thecore and electrode with a space between the electrode and the surrounding wall of the bore of the core, pouring into said space a non-metallic mineral powder, dry as to free water, containing water of combination that is not driven oil at the temperature to which it is subjected in the use of the plug, and having an angle of repose of not over 45", and compressing the powder in the space with suiiicient force to 86 compact it into a permanent holding body forming a gas tight joint with the opposed surfaces of the insulator and conductor, the filling and compressing being in successive layers which are sufficiently shallow to result in substantially uni- 4o form compacting of the powder without bridg n 4. The method of securing a rigid spark plug core in a metallic shell, which consists in placing the core in the shell with a space between their concentric surfaces, pouring into said space 'a u non-metallic mineral powder, dry as to free water, containing water of combination, and having an angle of repose of not over 15", and compacting the powder in the space into a permanent holding body fonning a gas-tight joint with said concentric surfaces.

5. The method of securing a rigid spark plug core in a metallic shell, which consists in assembling the core and shell with a shoulder of the core resting on a shoulder of the shell and an 66- annular space between the core and shell above said shoulders, pouring into saidspace a nonmetallic mineral powder, dry as to free water, containing water of combination, and having an angle of repose of not over 45?, and compacting 00 the powder in the space into a permanent holding body forming a gas-tight joint with the core and shell, and forming a water-tight sealtabove the compacted powder.

6. The method of securing a rigid spark plug corein a metallic shell, which consists in assembling the core and shell with a shoulder of the core resting on a shoulder .of the shell and an annular space between the core and shell above said shoulders, pouring'into said space a non- 70 metallic mineral powder, dry as to free water, containing water of combination, and an I angle of repose of not over 45', and compacting the powder in the space into a permanent holding body forming a gas-tight Joint with the core (I .and shell, fitting a ring above the compacted in place and forming sealing-and holding bodies. powder in substantially water-tight contact with 8. A spark plug comprising a ceramic insulat the shell and core, and turning over the upper ing core, a metallic shell around the core and edge 0! the shell and thereby forming a flange providing a substantially cylindrical space inside 5 holding the ring in place. the shell around the core, and powdercompacted 5 'l. A spark plug comprising an electrode, a insaid-space into a holding and sealing body. ceramic insulating core about the electrode. a 9 A spark plug in accordance with claim 8 metallic shell about said core, a seal between the and having a water-tight protection seal at the electrode and core and between the core and outer end of the compacted powder.

0 shell, said seals consisting of powder compacted O'l'lO C. ROEDE. 1o 

